1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a pattern on a photosensitive resin film in lithography, a method of forming a pattern for a semiconductor device, and a method of manufacturing a semiconductor device using the patterned film.
2. Description of the Related Art
In accordance with the progress of miniaturization of semiconductor devices, methods using, as etching masks, a plurality of patterned photosensitive resin layers stacked on each other have been proposed. In this method, exposure/development is performed twice or more. This can enhance resolution and margin for forming a desired fine pattern on a photosensitive resin film, compared to the case of forming a pattern by one-time execution of exposure/development. The pack-and-cover (PAC) process disclosed in U.S. Pat. No. 6,664,011B2 is one example of the methods.
When a plurality of patterned photosensitive resin layers are stacked by forming an upper photosensitive resin layer on a lower patterned photosensitive resin layer, the lower patterned photosensitive resin layer may be dissolved by a solvent contained in the upper photosensitive resin layer. To avoid this phenomena from occurring, a method has been proposed, in which after a pattern is formed of a lower photosensitive resin layer, the lower photosensitive resin layer is made insoluble before an upper photosensitive resin layer is formed thereon (see, for example, C. Chang et. al.; “Low Proximity Contact-holes Formation by Using Double Exposure Technology (DET)”, Proc. of SPIE, Vol. 5040, pp. 1241-1246, 2003).
As one method for making a lower photosensitive resin layer insoluble, ion implantation is known in the art. The above-mentioned publication discloses a technique of implanting ions into a lower photosensitive resin layer to harden its surface, and performing the above-mentioned PAC process, thereby forming a fine random contact-hole pattern that cannot be achieved by one-layer lithography process.